Engineering Calc Tools

Statics

Wall Bracket Calculator (Beam and Strut)

Strut force and wall pin reactions for a beam pinned to a wall and held by a strut, with a hook or pulley load.

Tool no.
ECT-S17
Rev
1.0
Updated
Oct 2026
Method
Frame analysis, two-force member
How to use this calculator

Put A at the wall pin of the beam. Enter the beam length to its end C, where the strut meets the beam (B) and how high above A the strut meets the wall (D; negative if below). Choose whether the end load hangs from a hook at C or from a cable that goes over a pulley at C and is tied to the wall level with the top of the pulley. With a pulley, say whether the load hangs on the cable itself or on a block pulley (two cable segments, the cable’s end tied back at C), which halves the cable tension. Add the beam’s weight or other loads if the problem has them.

Formulas

Moments about AFBD · b · h√(b² + h²) = Σ (load × distance from A)
Pin at AAx = FBD bBD (+ T for a pulley cable tied to the wall)  Ay = ΣP − FBD hBD

The strut is a two-force member: it is pinned at both ends and carries no load in between, so its force acts along the line BD. That turns the frame into a single rigid body with three unknowns.

Worked example

3 m beam, strut from 1.5 m to 2 m up the wall, 12 kN on a block pulley under a 0.3 m pulley (the default)

  1. The block pulley E hangs on two cable segments, so the cable tension is T = 12/2 = 6 kN.
  2. BD = √(1.5² + 2²) = 2.5 m, so the strut’s direction is (−0.6, 0.8).
  3. Moments about A: 6 × 3.3 + 6 × 3 − 6 × 0.3 = 36 kN·m. FBD × 1.5 × 0.8 = 36, so FBD = 30 kN (tension).
  4. Ax = 30 × 0.6 + 6 = 24 kN away from the wall; Ay = 12 − 30 × 0.8 = −12 kN (12 kN down).
  5. At D: Dx = −30 × 0.6 = −18 kN (toward the wall), Dy = 30 × 0.8 = 24 kN up.
  6. Check the whole frame: 24 − 18 − 6 = 0 horizontally, −12 + 24 − 12 = 0 vertically.

Assumptions and limits

  • The beam is horizontal and rigid, the pins are frictionless, and the strut and pulley are weightless.
  • In pulley mode, the cable leaves the pulley horizontally from its top and is tied to the wall.
  • For a beam held by a cable instead of a strut, use the beam reactions calculator.

Frequently asked questions

How do I know if BD is a strut or a tie?

Look at the sign. Positive means the member pulls (tension, a tie); negative means it pushes (compression, a strut). A diagonal running up to the wall above the beam is usually in tension; one running down to the wall below the beam is in compression.

Why does the pulley change Ax?

The cable is tied to the wall, so it pulls the beam-and-pulley toward the wall with the full tension. The pin at A has to push back the other way.